Vacuum cleaner motor-fan unit



May 26, 1959 J, COLE ET AL 2,888,192

VACUUM CLEANER MOTOR-FAN UNIT Filed Dec. 27, 1956 5 Sheets-Sheet 1 FANZnwWo/v F9. Z-A

INVENTORS,

JAMES D. COLE DUCKW/TZ BY ALBA-ET L. $680K Wag-M May 26, 1959 J. D. COLEE AL VACUUM CLEANER MOTOR-FAN UNIT Filed Dec.

3 Sheets-Sheet 2 INVENTORS. JAMES D. C045 Fee-o DUCKW/TZ y 44am?- 4.8680K J. D. COLE T l- VACUUM CLEANER MOTOR-FAN UNIT May 26, 1959 3'Sheets-Sheet 3 Filed Dec. 27, 1956 United States Patent VACUUM CLEANERMOTOR-FAN UNIT James D. Cole and Fred Duckwitz, Kent, and Albert L.Sebok, Akron, Ohio, assignors, by mesne assignments, to American Machineand Metals, Inc., New York, N.Y., a corporation of Delaware ApplicationDecember 27, 1956, Serial No. 630,805 22 Claims. (Cl. 230-117) Thepresent invention is concerned generally with an electric motor-fan unitfor vacuum cleaner applications and more particularly to such unitproviding novel structure determining the course of air flowtherethrough.

In vacuum cleaner units, the electric motor and fan structure of theprior art, still generally used, provides a flow path for the volume ofcleaning air passing first through the fan assembly and then from thefan exhaust through or around the motor for cooling the latter. Howeversome prior structures have provided for air flow in the reverse sense,that is first through or about the motor and then into the inlet of thesuction fan.

The present invention provides a novel structure for obtaining suchreverse air flow, here for the specific purpose of obtaining bettermotor ventilation by directing the moving air first through the motor oraround the motor elements before entering the fan assembly; and this ina durable structure adapted to simplicity in form and number ofelements, low cost mass production and excellent cooling in operation.The disclosed structure attains such motor cooling that at givenoperating conditions, the operating temperature is lowered markedly incomparison with units of similar rating and analogous structure whereinthe motor is cooled rather by a stream of cleaning air exhausting fromthe suction fan assembly. Consequently the entire unit may be given ahigher electrical rating insofar as operating characteristics areconcerned.

Furthermore in the fan assembly construction of the reverse flow unithere disclosed a novel type of fan assembly outlet or exhaust portconstruction is provided which in static operation, that is underconditions Where the'volume of cleaning air passing through the unit issubstantially zero, cuts down localized air recirculation into-and outof the fan chamber at the exhaust outlets and further presents arelatively smooth fan shell interior' aspect to the air mass rotatingtherein to minimize energy losses under the defined static operatingconditions. In consequence there is a lower load on the motor than isotherwise to be expected under static operating conditions in analogousunits without such outlet construction; and therefore higher speedoperation and a higher degree of static vacuum is obtainable. Suchresult is attained by mounting on the fan shell a plurality of elasticor resilient closure elements which automatically close upon the fanshell outlet openings as the volume of air passed therethroughdecreases, but which are easily displaced to variable open positions forpassage varying air volumes under the dynamic conditions of operation.

The general object of the invention is then to provide a reversed airflow electric motor and fan unit for a vacuum cleaner having relativelysimple durable structure adapted to low cost mass production. Another object is the provision of a vacuum cleaner motor fan unit adapted toprovide improved motor ventilation. A

further object is the provision of an outlet or exhaust,

structure in the fan assembly particularly adapted and useful in areversed flow electric-motor fan unit for a 2,888,192 Patented May 26,1959 vacuum cleaner, though having application in other fan assemblies.

Other objects and advantages will appear from the following descriptionand the drawings wherein:

Fig. 1 is a side view of a single stage vacuum cleaner unit embodyingthe invention, certain portions being; .partly in axial section andbroken away to show internal structure;

Fig. 1-A is a detail fragmentary view in section of the air outlet portstructure of the unit of Fig. 1;

Fig. 2 is a fragmentary view of a two stage vacuum cleaner unit showinga modification of the fan shell structure;

Fig. 2-A is an enlarged view showing in section the form of the annularrubber member appearing in the outlet port structure of Fig. 2;

Fig. 3 is a fragmentary view of a two stage unit showing a still furthermodification;

Fig. 3-A is an end view of the vacuum cleaner unit of Fig. 3; and

Fig. 4 is a fragmentary view showing a modification of the outletstructure appearing in Figs. 3 and 3-A.

The basic structure of the unit, appearing more fully in Fig. 1,comprises an electric motor M and fan as sembly F, the particular formdisclosed in the drawings being in wide sense similar to that appearingin, but arranged for air flow in a sense reverse to that of in the ColeU.S. Patent 1,713,455 of July 19, 1955 as well as having other pertinentdifferences hereinafter described.

Thus the motor includes one end or bearing bracket 10 fitted onto theend of the field core 11, having an integrally externally finned bearingsocket and also mounting the brushes in the case of a commutating motor;a

second end or bearing bracket 12 fitted onto the other end of the coreand having a disk-like radial extension 12a, which serves not only as anend wall of a fan chamber, but also as a support for a fan shell element13 mounted on its rim 12b; and a rotor or armature 14 supported inbearings slip fitted into the bearing sockets of brackets 10 and 12 withone end extending through bracket 12 into the fan assembly F. Suitablemeans (not shown) are provided to secure the end brackets and field coretogether; which (especially with a commutating motor) may as shown inthe aforementioned patent comprise bolts passed through arcuatelyslotted lugs projecting radially from the end bracket 10, and extendingexternally of the core into threaded engagement with the end bracket 12.

The end bracket 12 includes an integral centrally apertured, rearwardlyopen bearing socket formation 16 with the disk portion 12a extendingradially therefrom, and also integral field core engaging and spacingmeans 17 projecting from the rear of the disk. A plurality of angularlyspaced reinforcing or supporting webs 18 integrally join the rim 12b,means 17, disk portion 12a, and the joining portion whereby the" offsetrim is merged into the disk portion. 7 v j A cylindrical ring or (asshown) a plurality of cir cularlyspaced arcuat'e posts, rabbetedcoaxially with the bearing socket 16 to embrace and fit the outer edgeof the adjacent field core end circumferentially and end-' wise,'ar'eapt forms taken by means 17, whereby the bearing socket 16 and therewiththe disk 12a is mounted in spaced relation to the core. The outercircumference of the rim 1212, from each end in toward a radially pro-"jecting separating shoulder, is machined to provide cylin dricalsurfaces for mounting shell elements as later de= scribed.

In the fan assembly F, the fan shell 13 is a drawn sheet metal cuphaving a cylindrical wall portion 13a fitted onto the rim 12b and agenerally radial end wall 13b spaced from the front radial face of endbracket 12 to form therebetween a fan chamber. The cylindrical shellwall may be secured on the bracket y conventional means such as stakingthe wall inwardly at a few points into a recess or groove formed in therim periphery, or by screws threaded radially through the wall into therim.

A fan impeller of well known form and mounting, comprised of two axiallyspaced thin sheet metal disks 21 and 22 of equal diameter with curvedsheet metal blades or vanes 23 secured therebetween, is rotatablymounted within the fan chamber and clamped on the rotor shaft passedthrough a corresponding central aperture of disk 21 by a flanged spacersleeve 24-, clamping disk or washer 25 and clamping nut 26 threaded ontothe rotor shaft end. The flange of the sleeve 24 and the like sizedwasher 25 give radially extensive support to the central area of thedisk 21. With the sleeve 24 extending through the bearing socket centralaperture to abut against a shoulder provided by the inner face of abearing pressed onto the shaft, the impeller is held in selected axialand angular relation to the rotor, while the rotor and therewith theimpeller may be yieldably axially located in the unit by biasing thrustspring elements operatively interposed between the bearing socket endwalls and the bearings where the latter are slip fitted into theirrespective sockets.

Arcuate openings 29 in bracket 12 circumferentially spaced around socket16 form an air inlet structure from the motor interior to the impellerinlet opening provided by the larger central opening of annular disk 22.

To permit ready access to the shaft end region in the fan chamber duringassembly and fan balancing operations while attaining a desirablespacing of the shell radial end wall from the outer region of theimpeller, a centrally apertured circular portion 13c is dished or drawnoutwardly in the end wall, the inwardly flanged aperture therein beingclosed by a light press-fitted removable plug 28.

A second shell 30, formed of sheet metal with a short cylindrical wallor rim portion fitted onto the bracket rim 12b in manner similar to andopposite shell 15 and including a radial end wall with a central openingcomplementary to the peripheral shape of the core 11 and embracing thesame, among other functions, provides a closure between the end bracket12 and the core; whereby apart from any tolerated leakage, all airentering the fan is constrained to enter the brush end of the motorthrough the end bracket 10, thus initially passing over the finnedbearing socket structure therein, the brushes and commutator, betweenthe rotor and field core and around bearing socket 16.

Where a commutating motor is used as here shown, the shell 30 may serveto fix the core 11 against any relative rotational displacement duringbrush adjusting rotational shift of bracket 10, by engagement of itsradial end wall with the core, for example by a projection of the shellin an external longitudinal core groove 11a, or by non-circular form ofcore exterior to which the opening of shell 30 conforms.

As a part of the fan outlet or exhaust structure and also of structuremounting the unit in its environment of use, an elastic molded rubber orsynthetic plastic annular member 32 is fitted on the circumference ofthe fan assembly. In shells l3 and 30 the radial end walls merge throughcurved shell edge portions into the cylindrical walls, and an axialcross section of the annular member 32 as seen in Fig. 1 is more or lesschannelor U-shaped, so that the member 32 conforms to and embraces thefan assembly not only circumferentially but also overlaps an outer edgeportion of the radial walls in shells 13 and 30. Mounting rings or aplurality of circumferentially spaced paired mounting clips (for clarityof the drawing shown only in cross section by the dashed outline ele--ments A in Fig. 1) embrace the unit through mediation of member 32, theradial parts of the mounting elements being bolted to surroundingenvironmental structure. Where a mounting ring is used adjacent shell30, it may also serve as a partition separating an inlet air chamber ofa vacuum cleaner from an outlet chamber.

For the outlet structure of the fan chamber, a circumferentially spacedseries of square outlet ports or windows 35 are formed in thecylindrical wall 13a of shell 13, at a locus ofisct axially from the fanimpeller, to lie outward of the circumferential channel 33 formedbetween rim 12b and portion of bracket 12, and the cylindrical wall 13a,as a result of the rim olfset. Member 32 is molded with a broad flatbottomed circumferential groove in its cylindrical portion, providing aband 36 of reduced thickness wider than, and overlaying the locus of,windows 35. In the band 36, the thickness of which is emphasized in thedrawings for clarity, a series of similarly oriented identical squaredU-shaped incisions form flaps 37 each located to overlap a correspondingwindow 35 as shown in Fig. l-A and the lower half of Fig. l. The freeedge opposite the line of attachment or hinging of each flap is disposedon the side toward which the impeller rotates.

In consequence of such structure, under dynamic operating conditions,is. during actual cleaning flow air movement, the flaps 37 are displacedas indicated in Fig. lA, or in dashed lines 37 of Fig. 1, to allowescape of air in approximately tangential fashion from the fan chamber,the opening varying as required by the volume of air moved.

On the other hand under static conditions of operation, where no air orsubstantially no air is passing through the unit, the elastic flapsautomatically move to their normally closed postion, closing outletwindows 35 to prevent localized recirculation of air in and out of eachopening 35; and to present a relatively smoother interior aspect to thefan shell to the air being translated in a circular path within the fanchamber. Thus under static conditions those energy losses are minimizedthat would otherwise occur from local recirculation at open discharge oroutlet areas and through friction loss in the air moving around the fanchamber past open discharge areas. Hence the motor load is reduced; anda higher fan speed and higher degree of static vacuum may be obtainedwith a given commutating motor. Because of the better static vacuum thusobtainable, a single stage fan structure of acceptable diameter may beused in some applications where a two-stage assembly would have beenrequired.

Further the offset location of the fan chamber outlets relative to thefan blade tips minimizes the siren effect common in fan structures ofthis general type when fan shell apertures are located radially of thefan tips.

The incisions forming flaps 37 are shown as resulting from the actualshearing of a small amount of material out the band 36, as a simple wayof ensuring opening and complete closing of the flaps without hesitationby providing clearance between the flaps and the adjacent bandstructure. Also the flaps are shown as overlapping the edges of theopenings which thereby serve as stops for the closing motion of theflaps.

The form of member 32 not only provides a vibration absorbing structureto minimize sound transmission between the unit and environment, butalso is self-retaining in the contemplated use to prevent displacementof flaps 37 relative to windows 35 once the unit is assembled.

in the unit thus far described, not only does the strueture provideeffective motor ventilation by the air path through the motor towardfan, so that incoming cool air first ventilates the motor beforeentering the fan assembly, with excellent heat dissipation areas in themetal continuous with the bearing socket formations, as well as a novelair outlet structure for the fan assembly, but also it is adapted to lowcost durable construction, for example die casting of member 12 andfabrication of shell 13 by known sheet metal forming operations.

Modification of Fig. 2-

In' Figs. 2 and 2-A there appears in fragmentary view a second form offan assembly, wherein like numerals are used to designate elementsidentical with or closely similar to those of Fig. 1, and the motorstructure not appearing may be like to that of Fig. 1.

In this modification, a drawn sheet metal shell 213 secured on the rim21% of end bracket 212 and a shell 13 pressed in telescoped fit on thefirst shell provide first and second stage fan shells enclosingrespectively the identical impellers 220 and 20. In this Figure 2, noshell 30 appears, so that air may be drawn not only through the interiorof the motor but also around the exterior portions of the core 11between the spacing posts 17 integrally formed on bracket 212. The rim212b is not offset as in Fig. l, and further has a radial flange 212dwhereby the unit maybe bolted, clamped or otherwise suitably secured tosurrounding environmental structure.

The cylindric wall portion of fan shell 213 is reduced slightly at 213ato receive and provide a stop' shoulder for the shell 13 press fittedthereon, and is integrally joined by the tapered portion 2130 to theradial end wall 213b having a large central opening as an inlet to thesecond stage. A plurality of angularly spaced fi'x'ed'vanes 40, securedto the end wall 2131) and running from the tapered corner 213a inward tothe central discharge opening of the end wall, carry an annular plate 41circumferentially spaced from shell 213. A spool-shaped spacer sleeve 43is interposed on the rotor shaft between the first and second stageimpellers as part of the clamping means provided after the fashion ofFig. 1 by flanged sleeve 24, disk 25 and nut 26. The central opening ofplate 41 approaches the end region of sleeve 42 closely and the latterhas a circumferential groove curved in axial cross section to direct airthe more efficient'ly from the inner discharge ends of channelsformed-between vanes 40 into the inlet eye of the impeller 20.

I The second stage shell 13 is identical with that of Fig. l, with theaddition of a few elongated apertures 44 formed between adjacent outletopenings 35 at certain spaced locations for location of the elastic bandmember 232 providing a fan unit exhaust port control structure similarto that of member 32 in Fig. l. The axial section of member 232' isshown enlarged in Fig. 2-A. A series of recesses corresponding inspacing to shell windows'35 are molded in the outer surface of member232 to form panels236 of reduced thickness, which panels are cut to formflaps 37. A plurality of elongated beads 45 are molded on the innercylindrical surface of member 232 at locations corresponding to shellapertures 44, so that when the member 232 is stretched over andpositioned on the shell, beads 45 enter openings44 to retain the bandstructure in proper relation to the underlying shell.

Again in Fig. 2, the series of openings 35 are axially offset inlocusfrom the impeller 20 to avoid siren effect, and the tapered wall portion2130 in conjunction with the cylindrical portion of shell 13 forms acircumferential channel 233' just outward of impeller 20 receiving air.from the fan for discharge through the flap controlled or coveredwindows or discharge areas 35. The function of this discharge structureis that described for Fig-r1.

Modifications of Figs. 3 and 4 In Figs. 3 and 3-A there again appears atwo stage fan modification generally similar to Fig. 2, and having partslike to those of Figs. 1 or 2 bearing like reference numerals. The endbracket 212, the first and second stageimpellers 220 and 2G and clampingmeans therefor, the mounting of first and second stage fan shellelements 213 and 313 are identical with the corresponding items of Fig.2.

The principal change in Fig. 3 appears in the outlet port structure ofthe fan unit, which discharges endwise through end wall openings 335rather than-through the sidewall of shell 313. Accordingly the taper2130 of the first stage shell in Fig. 2 is omitted. The shell 313, whichmay be drawn with'a sharper corner between the radial. end andcylindrical wall portions, has a large round outwardly dished portionnot only to accommodatethe shaft end elements, but also to provide ashoulder 313a locating a flat rubber or elastic synthetic plasticannulus 332 covering the series of elongated arcuate openings 335 formedin the annular radial flat 31% outward of the shoulder 313:: at a sideposition adjacent to but just outward of the fan impeller periphery. Theinner face of band 332 is cemented to flat 3113b along; acircumferential locus lying inward of the openings 335. Thus the freeouter circumferential portion of the band serves as a flap varying theend outlet openings in manner similar to that of flaps 37 previouslydescribed.

Fig. 4 shows in rather schematic form a modification of the structure ofFig. 3 wherein a series of square outlet ope'nings 435 are formed in theshell 413, which otherwise is similar to 313. As in Fig. 3, a shoulder413a centers a flat elastic band 432, which however has incisionsforming flaps 437 covering windows 435 after the manner of Figs. 1 and2. In this case except for the flaps 437 the entire extent of band 432may be cemented to the annular radial flat lying outward of shoulder413a.

It is to be understood that the structure of Figs. 3 and 4 may besimplified to a single-stage fan structurewhere an end dischargingsingle-stage assembly is desired.

1'. In an electric motor-fan unit for a vacuum cleaner, wherein air isdrawn over motor elements for motor ventilation into the fan assembly,the structure comprising: a motor field core; a rotor therein having ashaft; a first end bracket and a second end bracket having bearingstherein for supporting the rotor shaft; the first bracket havingopenings therethrough to admit a ventilating. air stream to the interiorof the motor; the second end bracket being an integral structureincluding a centrally apertured disk with the rotor shaft projectingtherethrough, a bearing receiving socket formation open toward themotorward side thereof, a cylindrical rim portion carried at the edge ofthe disk, and supporting and spacing means extending from the disk tothe adjacent end of the core, the disk portion having apertures locatedbetween said socket and means as an air outlet from the motorinterior;centrifugal fan impeller means on the projecting shaft end having acentral opening adjacent the said outlet to receive air therefrom; andfan shell means secured on said rim portion forming with the sec ond endbracket an enclosure for said impeller means; said fan shell means beingprovided with a series of air exhausropnin s axially displaced from andradially out ward of the peripheral discharge region of said impellermeans 2. A structure as described in claim 1, wherein an end Wall ofsaid shell means opposite the rotor shaft end is provided with a centralopening with removable plug therein for access to the shaft end region.

3. A structure as described in claim 1, having second shell meansmounted on the said rim portion opposite the first named shell means,said second shell means having a radial wall portion extending inwardlyto embrace the core.

4. A structure as described in claim 1 wherein said impeller means is asingle stage impeller and said fan shell means is a cup-shaped elementwith cylindrical wall portion fitted on said rim portion, said rimportion is' axially ofiset toward the motor from said disk and joinedthereto by a tapered portion thereby to form a circumferential airchannel, and said series of air exhaust openings is formed in saidcylindrical wall at said channel.

5. A structure as described in claim 4, having secondshell means mountedon the said rim portion opposite the first named shell means, saidsecond shell means. having a radial wall portion extending inwardly toembrace the core.

6. In combination with the structure described in claim 5, a fan outletport structure comprising a band of elastic material surrounding thecylindrical shell Wall, said band having formed therein outlet flapseach corresponding in location to a respective air exhaust opening insaid cylindrical wall.

7. A structure as described in claim 6, wherein said band has endportions flanged inwardly to overlap outer marginal end portions of bothsaid shell means, whereby said band is retained in proper relation tothe shell exhaust openings, and the unit may be engaged between axiallyspaced mounting rings secured to surrounding environmental structure ina resilient mounting.

8. A structure as described in claim 1 wherein said fan shell meansincludes an end wall spaced endwise from said impeller means and has aseries of angularly spaced openings formed therein to provide saidexhaust openings, in combination with resilient outwardly opening outletcontrol fiap means secured on said wall.

9. The combination of claim 8, wherein said end wall includes a roundendwise projecting shoulder formation circumferentially spaced inwardfrom the outer edge of the shell to define a radial flat annularexternal area with said series of exhaust openings formed therein andwherein said flap means is provided by an annular elastomeric disksecured at its inner annular margin on said area.

10. A structure as described in claim 8, wherein said exhaust openingsare circularly arranged arcuate slots, and said flap means is an annularelastomeric disk overlapping said slots and secured along its innerannular margin to the end wall inwardly of said slots.

11. A structure as described in claim 8, wherein said outlet controlflap means comprises an elastomeric disk member overlapping said exhaustopenings and having incised therein a series of fiap formations disposedover the locus of said exhaust openings.

12. A structure as set forth inclaim 1, wherein said impeller meanscomprises a first and a second stage impeller and said shell meanscomprises a cylindrically and radially walled cup-shaped first stageshell with open end fitted on said rim portion and a cup-shaped secondstage fan shell having open end fitted in partially telescoped relationon the first stage shell; the end wall of the first stage shell having acentral opening as a discharge outlet to the second stage impeller and aplurality of air guide vanes secured thereto defining passageways fromthe peripheral region of the first stage impeller to said centralopening, and the cylindrical wall of the first stage shell being joinedto the end wall by a short tapered portion defining an annular channeladjacent the second stage shell; the second stage shell having a seriesof circumferentially spaced apertures axially offset from the secondstage impeller at a locus radially outward of said channel to providesaid exhaust openings; and a resilient band covering said exhaustopenings having a series of flaps incised therein each to cover arespective opening.

13. In an electric motor-fan unit for a vacuum cleaner, wherein theair-flow to the fan assembly is drawn over motor elements for motorventilation, the structure comprising: a motor field core; a rotortherein; a first end bracket and a second end bracket having bearingstherein for supporting the rotor shaft; the first bracket havingopenings therethrough to admit a ventilating air stream to the interiorof the motor; the second end bracket being an integral structureincluding a centrally apertured disk with the rotor shaft projectingtherethrough, a bearing receiving socket formation open toward themotorward side thereof, and supporting and spacing means extending fromthe disk to the adjacent end of the core, the disk portion havingapertures located between said socket and means as an air outlet fromthe motor interior; centrifugal fan impeller means on the projectingshaft end having a central opening adjacent the said outlet to receiveair therefrom; and fan shell means including a cup-shaped member with acylindrical wall and end wall; mounting means providing a cylindricalsurface to which the open end of the cup-shaped member is fitted formounting the latter on the periphery of said disk, the last said meansand cup-shaped member forming with the said disk an external enclosurefor said impeller means; said cupshaped member being provided in itscylindrical wall with a series of exhaust openings displaced axiallytoward the motor from, and radially outward of, the peripheral dischargeregion of said impeller means, said mounting means having a tapered wallportion inward of said cylindrical surface defining a circumferentialchannel receiving air from the impeller means for discharge through saidexhaust openings.

14. In combination with the structure described in claim 13, a fanoutlet port structure comprising a generally cylindrical band ofelastomeric material surrounding the cylindrical shell wall, said bandhaving formed therein outlet flaps each corresponding in location to arespective exhaust opening.

15. A structure as described in claim 14, wherein said band has integralspaced bead formations projecting from its inside cylindrical surfaceand the said cylindrical wall has correspondingly located aperturesreceiving the bead formations whereby said band is retained in properrelation to the shell exhaust openings.

16. In an electric motor-fan unit for a vacuum cleaner, wherein theair-flow to the fan assembly is drawn over motor elements for motorventilation, the structure comprising: a motor field core; a rotortherein; a first end bracket and a second end bracket having bearingstherein for supporting the rotor shaft; the first bracket havingopenings therethrough to admit a ventilating air stream to the interiorof the motor; the second end bracket being an integral structureincluding a centrally apertured disk with the rotor shaft projectingtherethrough, a bearing receiving socket formation open toward themotorward side thereof, and supporting and spacing means extending fromthe disk to the adjacent end of the core, the disk portion havingapertures located between said socket and means as an air outlet fromthe motor interior; centrifugal fan impeller means on the projectingshaft end having a central opening adjacent the said outlet to receiveair therefrom; and fan shell means including a cup-shaped member with acylindrical wall and end wall; mounting means providing a cylindricalsurface to which the open end of the cup-shaped member is fitted formounting the latter on the periphery of said disk, the last said meansand cup-shaped member forming with the said disk an external enclosurefor said impeller means; said cup-shaped member being provided in itscylindrical wall with a series of exhaust openings. I

17. A structure as set forth in claim 16, wherein said impeller meanscomprises a first and a second stage impeller and said shell meanscomprises a cylindrically and radially walled cup-shaped first stageshell with open end fitted on said rim and a second cup-shaped stage fanshell having open end fitted in partially telescoped relation on thefirst stage shell; the end wall of the first stage shell having acentral opening as a discharge outlet to the second stage impeller and aplurality of air guide vanes secured thereto defining passageways fromthe peripheral region of the first stage impeller to said centralopening, and the cylindrical wall of the first stage shell being joinedto the end wall by a short tapered portion defining an annular channelwith the second stage shell; the second stage shell having a series ofcircumferentially spaced apertures in the cylindrical wall of thecup-shaped member to provide said exhaust openings; and a resilient bandcovering said exhaust openings having a series of U-shaped incisionstherein to'form like oriented flaps each to cover a respective exhaustopening and disposed to open outwardly toward the direction of impellerrotation.

18. In an electric motor driven vacuum cleaner fan assembly having acentrifugal impeller and a cylindrical cup-shaped fan housing memberabout the impeller, fan housing exhaust structure comprising: anangularly spaced circumferential series of exhaust openings formed in acylindrical wall portion of said member, and elastomeric flap meanssecured on said member to cover the openings therein and being outwardlydisplaceable, with edges of the openings overlapped by said flap means.

19. In an electric motor driven vacuum cleaner fan assembly having acentrifugal impeller and acylindrical cup-shaped fan housing memberabout the impeller, fan housing exhaust structure comprising: acircumferentially spaced series of exhaust openings formed in an endwall portion of said member, and a flat annular elastomeric elementsecured to said member to cover the openings therein and formingoutwardly displaceable flap means, with the opening edges overlapped bysaid fiap means.

20. In an electric motor driven vacuum cleaner fan assembly having acentrifugal impeller and a cylindrical fan housing about the impellerprovided with fan housing exhaust openings, fan housing exhauststructure comprising: a series of exhaust openings circumferentiallyspaced in a wall portion of the said housing, and an annular member offlexible elastomeric material covering said series to form control flapmeans for said openings, said flap means being outwardly displaceablevariably under varying exhaust air flow and self-returning to a closedposition closing said openings upon cessation of flow through saidopenings.

21. In an electric motor driven vacuum cleaner fan assembly having acentrifugal impeller and a cylindrical cup-shaped fan housing memberabout the impeller fan housing exhaust structure comprising: acircumferentially spaced series of square exhaust openings formed in acylindrical wall portion of said member, and a cylindrically annularelastomeric band stretched over said member to cover the openings andhaving a series of incisions therein forming outwardly displaceableflaps, each with free edges overlapping the edges of a correspondingopening.

22. In an electric motor driven vacuum cleaner fan assembly having acentrifugal impeller and a cylindrical fan housing about the impellerprovided with fan housing exhaust openings, fan housing exhauststructure comprising: a series of exhaust openings circumferentiallyspaced in a wall portion of the said housing, and an annular elastomericmember disposed over said series and incised to form control fiapmeansfor said openings, said flap means being outwardly displaceable variablyunder varying exhaust air flow and self-returning to a closed positionclosing said openings upon termination of flow through said openings.

References Cited in the file of this patent UNITED STATES PATENTS2,778,563 Doyle Jan. 22, 1957 FOREIGN PATENTS 10,605 Great Britain May4, 1912 811,248 France Apr. 9, 1937

